We propose to develop novel soluble sensing materials that can be used in homogenous fluorescence assays for the detection of Yersinia pestis antigens and antibodies. Y. pestis is the etiological cause of plague and a potential biowarfare agent. The sensing materials are solutions of functionalized liposomes that become fluorescent when they bind selectively to the antibody targets. The solutions will be used to develop both competitive assays for detection of the Y. pestis F1 antigen and direct one-step assays for the detection of Y. pestis antibodies that can be performed in commonly available plate readers. Swift identification of a Y. pestis infection is very important to insure timely and appropriate treatment. Current methods of diagnosis (culture, fluorescent antibody staining, agglutination tests) are slow, complicated, require trained personnel and are not suitable for screening large numbers of samples quickly, in the advent of a biological attack. ELISA and PCR methods for detection of Y. pestis infection are in development, however, these methods also require multiple steps, expensive reagents and/or equipment. The assays developed from our sensing materials will be inexpensive, reliable, simple and swift. The materials will subsequently be adapted for detection of antibody response to other diseases, for medical diagnostics and vaccine research.